You're giving Abby way too much credit here. Most twelve year olds (or younger) would see people getting choked out/having their lives threatened as a dangerous situation and to get as far away as possible.

Abby - instead - wants to follow the person who was doing the choking because she doesn't like what her brother did.

Teddi wasn’t injected. You’ll note we never see the needle contact the skin. Plus she’s been shown looking at the needle contemplating whether or to to go through with it. Also, they only assume it will turn him male. Shape shifting may not be something angels can do in this universe.

You're giving Abby way too much credit here. Most twelve year olds (or younger) would see people getting choked out/having their lives threatened as a dangerous situation and to get as far away as possible.

Abby - instead - wants to follow the person who was doing the choking because she doesn't like what her brother did.

No, but to make things interesting they usually are. Consider Dawn from Buffy the Vampire Slayer. The mystics turned a universal key into a kid sister Buffy would protect. That actually makes sense, but for the sake of making everything interesting the writers couldn't make her a studious girl who wants to avoid danger, but a little brat that constantly gets into trouble. How many plots would never happen in this webcomic if Abby wasn't a brat?

Perhaps now Teddi will seek out Chloe since she really is the lesser of two evils as far as teaching Abby to control her powers.

How many plots would never happen in this webcomic if Abby wasn't a brat?

I don't mind her being depicted as a brat so much as I mind her being depicted as incredibly out of touch, ignorant, idiotic etc. for someone her age and in her situation. Yes kids can be ignorant but she passes from that into extreme obliviousness.